This invention relates to an exhaust gas control means for an engine and more particularly to an improved exhaust gas valve arrangement that improves the engine performance.
A well known expedient for increasing the output of an internal combustion engine is to employ large degrees of valve overlap so as to improve the breathing capacity of the engine at high speeds. However, as is well known, engines having high degrees of valve overlap tend to have poor low speed and mid range performance. It has been discovered that one reason for this poor mid range performance is the formation of pulses in the exhaust gases which tend to pass back into the combustion chamber during the period of valve overlap and cause the exhaust gases to flow outwardly through the intake passage thus precluding the induction of a proper fuel air mixture for smooth running.
As is disclosed in the copending patent applications of Hideaki Ueda, entitled "High Performance Exhaust Systems For Internal Combustion Engine", Serials Nos. 935,340 and 935,342, filed Nov. 26, 1986, and assigned to the assignee of this application, it has been found that these poor mid range running conditions may be overcome through the use of a reflective valve that is disposed in the exhaust pipe between the exhaust ports and an expansion chamber. By appropriately positioning these reflective valves in response to the engine running characteristics, the effects of the exhaust pulses in causing reduced induction can be overcome and performance significantly improved.
In accordance with the arrangement shown in those patent applications, it is desirable to provide an individual reflective valve in each of the exhaust pipes of the engine. This, however, can cause certain problems in connection with design and operation. If individual operators are provided for each of the reflective exhaust valves, the system becomes very complicated and placement of all of the associated components can be difficult. However, if all of the valves are affixed for rotation with a common valve shaft, there are a number of other disadvantages which can arise. Because of the fact that the valve shaft passes through the exhaust pipes, expansion can become a problem. Furthermore, the longer the shaft becomes, the greater the expansion problems are.
Also, if the valves are all affixed to a common valve shaft, then the placement of the valves becomes interdependent and it may not be possible to place all of the valves at the optimum location. In addition to this disadvantage, the placement of all of the valves on a common valve shaft dictates that the exhaust pipes must also run parallel to each other in the area of this valve shaft. This is not always desirable or possible.
It is, therefore, a principal object of this invention to provide an improved exhaust gas control means for an engine.
It is a further object of this invention to provide an arrangement for operating a plurality of exhaust control valves simultaneously without necessitating their all being carried by a common shaft.
It is a further object of this invention to provide a multiple exhaust gas control valve arrangement wherein there is greater latitude in the positioning of the individual valves while at the same time maintaining common control for them.
It is yet another object of this invention to provide an interrelated exhaust control valve arrangement for an engine wherein the valves may be placed at different axial locations relative to each other.